United States Published Patent Application 2005/0138919 A1 (Nakano et al.) discloses an apparatus for introducing secondary air into an automotive exhaust at a location on an upstream side of the catalytic converter in the exhaust pipe. In this reference, the airflow rate is controlled by an electronic control unit based on a difference between secondary air supply pressure and a shutoff pressure. The purpose of such a system is to decrease undesirable deterioration and exhaust emissions. While not stated in this reference, such a system is important at vehicle startup to increase the airflow in the exhaust, to thereby decrease the light-off time for the emissions catalyst, and the airflow rate must be regulated in accordance with Title 13 California Code Regulations Section 1968.2, Section E, Rule 5.2.1. Unfortunately, raw pressure values vary widely over time, and it has been the practice to average system pressure pulsations over time to produce a system pressure, but this approach is unable to take into account variations in system pressure pulsations and effects that such a factor can have on airflow rates.